This invention relates to food containers, particularly a food container which may be disposable, and more particularly a food container which comprises multiple plies.
Disposable food containers are well known in the art. Disposable food containers include common paper plates, bowls, clam shells, trays, etc.
The art has paid considerable attention to making, molding, and deforming these food containers out of a single plane. In this latter process a blank is provided. The blank is inserted between mating platens and pressed. The blank may have radial grooves at its periphery. The radial grooves provide for accumulation of the material deformed by the platens. Exemplary art includes U.S. Pat. No. 3,033,434, issued May 8, 1962 to Carson; U.S. Pat. No. 4,026,458, issued May 31, 1977 to Morris et al., the disclosures of which are incorporated herein by reference; U.S. Pat. No. 4,606,496, issued Aug. 19, 1986 to Marx et al.; U.S. Pat. No. 4,609,140, issued Sep. 2, 1986 to van Handel et al.; U.S. Pat. No. 4,721,500, issued Jan. 26, 1988 to van Handel et al.; U.S. Pat. No. 5,230,939, issued Jul. 27, 1993 to Baum; and U.S. Pat. No. 5,326,020, issued Jul. 5, 1994 to Cheshire et al.
The blanks are typically comprised of paperboard, and more particularly a single sheet of paperboard, as illustrated in the aforementioned patents. A single sheet of paperboard is utilized due to the belief that to deform the blank out of its plane the blank must be thin and of a single ply. The paperboard, or other material used for the blank, is typically substantially homogeneous, as illustrated by U.S. Pat. No. 4,721,499 issued Jan. 26, 1988 to Marx et al. It is believed that homogeneity aids in the radially symmetric deformation of round food containers, such as plates and bowls.
However, these attempts in the art suffer from several drawbacks. As illustrated by the plethora of attempts to improve the rigidity and stability of the food containers, the prior art attempts do not provide food containers of sufficient strength. This lack of strength leads to spillage of food when the food container becomes overloaded, or, alternatively, unduly constrains the amount of foods which can be placed on the food container at a given time.
Yet another disadvantage occurs with the single ply paperboard food containers of the prior art. The relatively thin single ply paperboard provides only minimal thermal insulation. When warm food is placed on the food container, little insulation is provided, allowing the food to cool. Cooling occurs due to heat transfer through the food container to the surface below, or to the atmosphere.
What is needed in the art, therefore, is a food container providing increased strength, rigidity, and thermal insulation. One potential solution is to increase the thickness of the blank. However, this increase is accompanied by an often unacceptable increase in material costs, since the material costs are proportional to the basis weight of the blank.
Thus, there exists a need in the art for a food container having the aforementioned properties but without undue material costs. Furthermore, the blank for such a food container must be readily deformable out of its plane.
One attempt in the art to overcome this trade off is to use multi-ply laminate food containers. For example, it is known in the art to make food containers out of corrugated laminates. Such food containers have panels which are typically scored and folded as illustrated by U.S. Pat. No. 5,205,476 issued Apr. 27, 1993 to Sorenson. However, this scored and folded food containers require a costly folding apparatus and are inherently unreliable. Adjacent panels in the food container are defined by cuts or score lines. The adjacent panels are then foldably connected. After adjacent panels are foldably connected, they must be adhesively joined or mechanically interlocked to remain in place. The adhesive and its associated application apparatus represent additional capital costs and ongoing material costs. Mechanical materials have tabs. The tabs require cutting/slitting operations and are inherently unreliable. The tabs become disengaged, torn, or simply misaligned.
One attempt in the art to overcome this deficiency is to use single faced corrugated materials and continuously form rather than score, cut and fold the food container as illustrated by U.S. Pat. No. 5,577,989 issued Nov. 26, 1996 to Neary. Continuously formed food containers have peripheral sections which are raised gradually and continuously through a transition area relative to the central region of the food container. However, single faced corrugated materials have neither the strength nor the insulating capability of three ply corrugated materials. Neary acknowledges that the industry had been unable to create a satisfactory unitary construnction by stamping corrugated paperboard of more than two plies.
However, these deficiencies in the prior art are overcome by the present invention. The present invention provides multi-planar food containers made, in one embodiment, of three ply corrugated materials without relying upon the score, cut and fold techniques of the prior art.